Drilling tool, in particular spiral drill

ABSTRACT

In a drilling tool, in particular a spiral drill, in particular for drilling rock, comprising a tool-side fastening end, a workpiece-side cutting end and an interposed cutting part comprising at least one main helical groove extending along the cutting part, which is defined by a substantially constant helix pitch, and at least one partially cylindrical and/or partially conical helix web outer face extending along the cutting part, defined by at least one main helical groove, it is provided that a plurality of groove sections are formed in the helix web outer face, which extend transversely to the direction of the pitch of the main helical groove.

The invention relates to a drilling tool, in particular a spiral drill,in particular for drilling rock. Such a drilling tool is usuallyshaft-shaped, wherein in most cases, the outer side of an initial shaftis uniformly cylindrical. A fastening end of the drilling tool can alsobe conical in order to fix a particularly accurate axial position of thedrilling tool relative to the drilling drive.

The drilling tool is usually provided with a cutting end or drillinghead which is possibly reinforced by a hard metal plate which isinserted in a slot at the cutting end of the drilling tool and fastened.The drilling head or the cutting end are characterised by a main cuttingangle which usually lies between 100° and 150°.

When positioning the drilling tool, the cutting end initially engages inthe workpiece and as drilling is continued, a cutting part locatedbetween the fastening end and the cutting end comes into engagement withthe workpiece, whereby a cylindrical hole is cleared in the workpiece.

The cutting part forming the predominant part of the drilling toolusually has two main helical grooves extending along the cutting part,via which the drilling dust is to be removed from the cutting end.Furthermore, the known cutting part forms a partially cylindrical orpartially conical helix web outer face extending along the cutting part,defined by the two main helical grooves, which usually extends with thesame pitch parallel and between two main helical grooves. From thepartially cylindrical helix web outer face, the cutting part is formedwith a step-shaped profile jump at the transition to the respective mainhelical groove, by which means a helically extending edge or cuttingedge is formed. On viewing the cross-section of the drill, the helix webouter face runs along the constant outside diameter of the cylindricalshaft base body of the drilling tool. Various types of drilling tool areknown to increase the drilling efficiency of the drilling tool. Knownfrom DE 20 2005 016 682 U1, for example, is a drilling tool whose mainhelical groove is stepped at its groove flank facing the drilling head.The individual steps run with the same pitch within the main helicalgroove.

EP 0 685 629 B1 discloses a rock drill in which two parallel removalflutes are incorporated in the drill shaft. In this way, twoparallel-running removal flutes having different flute cross-sectionsshould be provided.

Known from DE 297 23 908 U1 is a rock drill a main helical groovedivided into a plurality of parallel-running, separate drilling groovesections, wherein the drilling groove sections are either separated byannular elevations or corresponding indentations, each having the samepitch. DE 103 42 817 A1 discloses a drill having a main helical groovein which a plurality of helical, annular projections running parallel tothe main helical groove are incorporated, forming a plurality ofdrilling groove sections of parallel profile.

All the known aforesaid drilling tool designs suffer from thedisadvantage that the strength of the drilling tool is significantlyimpaired by the additional profiling to form larger or separate helicaldrilling grooves. As a result of the additional helical groove sections,stress peaks are formed at the cutting part of the drilling tool definedby the helical groove sections and the concomitant weakening of thematerial, which stress peaks can lead to premature failure of thedrilling tool.

It is the object of the invention to overcome the disadvantages of theprior art, in particular to further develop a drilling tool of thegeneric type in such a manner that the drilling efficiency is increasedwithout impairing the fatigue strength of the drilling tool.

This object is achieved by the features of patent claim 1.

According to the invention, a plurality of groove sections areincorporated in the partially cylindrical helix web outer face, inparticular on one or several imaginary helical tracks around the cuttingpart of the drilling tool, which groove sections extend transversely orat an appreciable angle, in particular of 200 to 900, to the directionof the pitch of the main helical groove. The individual groove sectionspreferably run rectilinearly on the helix web outer surface and inparticular have a constant groove radial depth and/or groove widthand/or groove length. The plurality of groove sections can lieconcentrically to the longitudinal axis of the drilling tool on a closedannular track. An arrangement of the plurality of groove sections alongone or more imaginary helical tracks has provide more advantageous,particularly compared to the arrangement of the plurality of groovesections on a closed annular track, in that the fatigue strength ishigher in the helical-track-like arrangement. It was shown that in thearrangement of the groove sections on a closed annular track, the stresspeaks induced during operation in the material delimiting the pluralityof groove sections are higher than in the helical-track-like arrangementof the plurality of grooves. Tests have shown that the drillingefficiency can be increased significantly with the measure according tothe invention. The plurality of groove sections located transversely tothe main helical groove in the helix web outer face effect a significantreduction in the friction between the workpiece and the drilling tool,wherein on the one hand, less drive energy needs to be introduced intothe drilling tool and on the other hand, the drilling tool is far lessthermally loaded. It was also shown that no adverse influence on thefatigue strength of the drilling tool is noticeable due to the groovesections according to the invention in the helix web outer face wherethe drilling tool is configured to be the strongest in some sections.

In a preferred embodiment of the invention, the plurality of groovesections extend with a substantially greater circumferential directioncomponent than axial direction component. It is clear that the annularsections can also extend exclusively in the axial direction. It wasshown, however, that a dominant circumferential direction component ismore advantageous in regard to the drilling efficiency.

In a preferred embodiment of the invention, the plurality of groovesections are arranged parallel to one another. As a result of theparallel arrangement and the spacing of the plurality of groove sectionsfrom one another necessarily incurred, it is possible to increase thedrilling dust removal effect of the plurality of grooves withoutweakening the drilling tool too severely.

The plurality of groove sections preferably each extend from an edge ofthe main helical groove facing the cutting end to an edge of the mainhelical groove facing the fastening end, in particular linearlycircumferentially. They preferably extend from one edge to the other onthe shortest path along the helix web outer face.

In a preferred further development of the invention, the plurality ofgroove sections lie on at least one common auxiliary helical track whosepitch is smaller than the pitch of the main helical groove. The helixpitch is defined by an axial width (in mm) of a full-circumference 3600revolution of the helix. The pitch of the at least one auxiliary helicaltrack is preferably smaller than the pitch of the main helical groove insuch a manner that the helical course of the auxiliary helical trackduring one revolution is interrupted at least once, preferably severaltimes, in particular more than five to ten times, by the main helicalgroove. In this arrangement of the plurality of groove sections on asingle helical track extending along the drilling tool, of differentpitch to the pitch of the main helical groove, optimal fatigue strengthresults were achieved, whereby the drilling efficiency can be increasedas a result of improved removal of drilling dust and a reduction in thethermal loading of the drilling tool.

In a preferred embodiment of the invention, the pitch of the mainhelical track is at least twice, in particular five times, preferablyten times, in particular twelve or fifteen times larger than the helixpitch of the imaginary auxiliary helical track on which the plurality ofgroove sections inserted exclusively in the helix web outer face arepositioned.

The helix pitch of the imaginary auxiliary helical track and/or thehelix pitch of the main helical groove preferably remain constant alongthe total axial extension of the cutting part. In this way,substantially continuous and blockage-free removal of drilling dust canbe achieved along the main helical groove and the plurality of groovesections.

In a preferred embodiment of the invention if a diameter of thecylindrical shaft base body of the drilling tool, in particular thepartially cylindrical helix web outer face is 5 mm, 6 mm, 6.5 mm, 7 mm,8 mm, 9 mm or 10 mm, a helix pitch of the auxiliary helical track in arange of 0.5 mm to 3 mm, preferably of 1 mm to 2.5 mm, preferably of 1.5to 2 mm is selected. In this case, in particular the helix pitch of themain helical groove is determined in a range of 15 mm to 40 mm,preferably of 20 mm to 30 mm.

In a further development of the invention, a width of the plurality ofgroove sections and/or a radial depth of the plurality of groovesections is smaller than a groove width of the main helical groove or aradial depth of the main helical groove. The groove width is definedfrom the shortest distance between two opposing edges of the mainhelical groove at the radial level of the cylindrical outer web facebetween two main helical grooves. The radial depth of the main helicalgroove is defined by the radial distance of its radial low to thepartially cylindrical outer web face between two adjacent main helicalgrooves.

A radial depth of the plurality of groove sections is preferably lessthan 1 mm, preferably less than 0.5 mm, in particular equal to 0.1 mm. Awidth of the plurality of groove sections can be less than 1 mm, inparticular equal to about 0.5 mm, 0.6 mm or 0.7 mm.

In a preferred embodiment of the invention, the plurality of groovesections lie interrupted by the at least one main helical groove on animaginary (uninterrupted) auxiliary helical track. The auxiliary helicaltrack covering the plurality of groove sections winds in particularsubstantially over then entire axial length of the cutting part.

The auxiliary helical track covering the plurality of grooved sectionspreferably opens substantially into the drilling end, wherein either oneof the groove sections opens at the drilling end or at least in a veryclose proximity to the drilling end.

In a further development of the invention, each groove section opensfrom a main helical groove edge into the adjacent, opposing main helicalgroove edge.

In a further development of the invention, the helix pitch direction ofthe imaginary auxiliary helical track is either in the oppositedirection to or preferably in the same direction as the helix pitchdirection of the main helical groove.

Further properties, features and advantages of the invention will becomeapparent from the following description of a preferred embodiment of theinvention with reference to the appended drawings, in which:

FIG. 1 shows a side view of a drilling tool according to the invention;and

FIG. 2 shows a cross-sectional view of the drilling tool according toFIG. 1 along the line of intersection II-II.

In FIGS. 1 and 2, the spiral drill according to the invention isgenerally provided with the reference numeral 1. The spiral drill 1 hasa substantially cylindrical basic shaft form.

The spiral drill 1 forms a fastening end 3 which is designed to becylindrical and has recesses 5, 7 at the end in order to ensure adefined position with regard to the drilling tool drive (not shown). Thecylindrical fastening end 3 extends substantially over a quarter to athird of the total length of the spiral drill 1.

In the axial direction X, the fastening end 3 is followed by the cuttingpart 11 whose maximum cylindrical outside diameter is slightly smallerthan that of the fastening end 3.

In the ideally cylindrical base body of the cutting part 11 at thebeginning of the production process of the spiral drill, twoparallel-running spiral main helical grooves 13, 15 are incorporated,which extend with constant pitch along the cutting part 11 to a drillinghead or cutting end 17 of the spiral drill 1, which defines at least twomain cutting edges.

Between the main helical grooves 13, 15 there remain two partiallycylindrical helix web outer faces 21, 23 of the cylindrical base body ofthe cutting part, which are spaced apart from one another by a mainhelical groove 13, 15 and run parallel to one another, and have the samepitch as the two main helical grooves 13, 15. The width (shortestdistance between two opposing boundary edges of a helix web outer face21, 23) of each helix web outer face 21, 23 substantially corresponds tothe width (shortest distance between the opposing edges defining themain helical groove 13, 15) of the main helical groove 13, 15. The helixpitch (axial width in the case of a full-circumference 360° revolutionof the helix) of the helix web outer faces 21, 23 and the main helicalgrooves 13, 15 is about 20 to 30 mm.

In both partially cylindrical helix web outer faces 21, 23, aninterrupted auxiliary helical track can be identified, formed by aplurality of equal-length groove sections 27. The groove sections 27cover the constant-pitch auxiliary helical track and the plurality ofgroove sections 27 are indicated in alignment with one another relativeto the revolution of the auxiliary helical track. The helix pitch of theplurality of groove sections 27 is significantly smaller than that ofthe main helical grooves 13, 15 or the helix web outer faces 21, 23.

The constant helix pitch of the interrupted auxiliary helical track isabout 1.5 to 2 mm for a 360° revolution. Each groove section 27 of theauxiliary helical track has a radial depth of about 0.1 mm and a widthof about 0.5 to 0.7 mm.

The individual groove sections 27 lie parallel to one another and have asignificantly larger circumferential direction component than axialdirection component. The circumferential direction component is slightlysmaller than a right angle to the axial direction X.

As can be seen in FIG. 1, each groove section 27 opens at an angle of30° to 60° at the transition edge between the helix web outer face 21,23 and the respective main helical groove 13, 15 into the main helicalgroove 13, 15 which is indicated in FIG. 2 by the asymmetrical noseopening of the groove sections 27. As can be seen in FIG. 2, both mainhelical grooves 13, 15 have a convex groove base.

As a result of the small helix pitch, the auxiliary helical track isinterrupted several times by the main helical groove 13, 15, whereineach groove section 27 of the auxiliary helical track opens from a mainhelical groove edge into the opposing edge, extending continuously freefrom kinks.

It was shown that with the auxiliary helical track defined by the groovesections 27 having the same pitch direction in relation to the pitchdirection of the main helical groove, the removal of drilling dust canbe increased and the friction between the helix web outer face and theworkpiece can be significantly reduced. The removal of heat from thedrilling tools is also improved by the fan-like arrangement ofinterrupted groove sections 27 according to the invention because thegroove sections effect cooling by producing air turbulence at the outerside of the spiral drill 1.

The features disclosed in the preceding description, the figures and theclaims can be important both singly and in any combination forimplementing the invention in the different embodiments.

REFERENCE LIST

-   1 Spiral drill-   3 Fastening end-   5, 7 Recesses-   11 Cutting part-   13, 15 Main helical groove-   17 Cutting end-   21, 23 Helix web outer faces-   27 Groove sections-   x Axial direction

1. A drilling tool, in particular a spiral drill, in particular fordrilling rock, comprising a tool-side fastening end, a workpiece-sidecutting end and an interposed cutting part comprising at least one mainhelical groove extending along the cutting part, which is defined by asubstantially constant helix pitch, and at least one partiallycylindrical and/or partially conical helix web outer face extendingalong the cutting part, defined by said at least one main helicalgroove, characterised in that a plurality of groove sections are formedin the helix web outer face, which extend transversely to the directionof the pitch of the main helical groove.
 2. The drilling tool accordingto claim 1, characterised in that the plurality of groove sections arearranged parallel to one another.
 3. The drilling tool according toclaim 1 or 2, characterised in that the plurality of groove sectionseach extend from an edge of the main helical groove facing the cuttingend to an edge of the main helical groove facing the fastening end. 4.The drilling tool according to any one of the preceding claims,characterised in that the plurality of groove sections lie on at leastone common auxiliary helical track whose pitch is smaller than the pitchof the main helical groove.
 5. The drilling tool according to claim 4,characterised in that the pitch of the at least one auxiliary helicaltrack is smaller than the pitch of the main helical groove in such amanner that the helical course of the auxiliary helical track during onerevolution is interrupted at least once, preferably several times, inparticular more than five to ten times, by the main helical groove. 6.The drilling tool according to claim 4 or 5, characterised in that thepitch of the main helical track is at least twice, in particular fivetimes, preferably ten times, in particular twelve or fifteen timeslarger than the pitch of the auxiliary helical track.
 7. The drillingtool according to any one of claims 4 to 6, characterised in that thepitch of the auxiliary helical track and/or the at least one pitch ofthe main helical groove remain unchanged along the cutting part (11). 8.The drilling tool according to any one of claims 4 to 7, characterisedin that if a diameter of the drilling tool is 5 mm, 6 mm, 6.5 mm, 7 mm,8 mm, 9 mm or 10 mm, a pitch of the auxiliary helical track in a rangeof 0.5 mm to 3 mm, preferably of 1 mm to 2.5 mm, preferably of 1.5 to 2mm is selected, wherein in particular the pitch of the main helicalgroove is selected in a range of 15 mm to 40 mm, preferably of 20 mm to30 mm.
 9. The drilling tool according to any one of the precedingclaims, characterised in that a width of the plurality of groovesections and/or a radial depth of the plurality of groove sections issmaller than a width of the main helical groove or a depth of the mainhelical groove.
 10. The drilling tool according to any one of thepreceding claims, characterised in that a radial depth of the pluralityof groove sections is less than 1 mm, preferably less than 0.5 mm, inparticular equal to about 0.1 mm.
 11. The drilling tool according to anyone of the preceding claims, characterised in that a width of theplurality of groove sections is less than 1 mm, in particular equal toabout 0.5 mm, 0.6 mm or 0.7 mm.
 12. The drilling tool according to anyone of the preceding claims, characterised in that the plurality ofgroove sections lie interrupted by the at least one main helical grooveon an auxiliary helical track, wherein the auxiliary helical trackdefined by the plurality of groove sections winds in particular inconstant pitch substantially over then entire axial length of thecutting part.
 13. The drilling tool according to claim 9, characterisedin that the auxiliary helical track forming the plurality of groovedsections substantially opens into the drilling end.
 14. The drillingtool according to any one of the preceding claims, characterised in thateach groove section opens from a main helical groove edge into theopposing main helical groove edge.
 15. The drilling tool according toany one of the preceding claims, characterised in that the pitchdirection of the auxiliary helical track is in the opposite direction toor preferably in the same direction as the pitch direction of the mainhelical groove.